§1.1 Field of the Invention
The present invention concerns the use of whispering gallery mode (“WGM”) sensors together with a microfluidic device, such as a syringe for example, to detect the presence of, identify the composition of, and/or measure an amount or concentration of substances (referred to generally as “target entities” or “target analytes”), such as chemical or biological entities.
§1.2 Background Information
There exists an ongoing need for sensors for detecting various “target entities” such as, for example, infectious agents (e.g., viruses, bacteria, etc.), toxins, small amounts of proteins, DNA, RNA, etc. Similarly, there exists an ongoing need for sensors for measuring DNA hybridization, protein adsorption, biomolecular mass, etc.
One known device used to detect the presence of small particles is a microsphere sensor coupled to an optical waveguide (e.g., an eroded optical fiber), one end of which is optically coupled with a light source and the other end with a light detector. Whispering gallery modes of the light circulating within the microsphere can be observed in optical signals detected at the detector. Target entities selectively captured (e.g., adsorbed) by target receptors on the surface of the microsphere may shift the whispering gallery modes. These so-called WGM sensors have emerged as an important optical tool for detection and analysis of trace quantities of biological materials. These WGM sensors have been employed in a host of applications including the detection of virus and bacteria, measurement of DNA hybridization and protein adsorption, and biomolecular mass determination.
Examples of such WGM sensors are described in U.S. Pat. No. 7,491,491 (referred to as “the '491 patent” and incorporated herein by reference) and U.S. Pat. No. 7,841,173 (referred to as “the '173 patent” and incorporated herein by reference). Although the '491 and '173 patents mainly describe microsphere-based WGM sensors, such sensors may employ microresonators (referred to generally as “resonators”) with geometries other than microspheres, such as, for example, (micro-)cylinders, (micro-)rings, (micro-)disks, (micro-)toroids, (micro-)racetracks, (micro-)bottle resonators, and any other geometry capable of supporting WGM. Each of these configurations relies on the inherent sensitivity of the WGM resonances within the resonator to changes in the external environment to provide a sensitive detection mechanism.
U.S. Patent Application Publication Number US-2010-0297363-A1 (referred to as “the '363 publication” and incorporated herein by reference) describes fabricating more sensitive WGM sensors.
It would be useful to use sensors, such as those introduced above, to test small volumes of fluid. It would be useful to test very small volumes of fluid, such as less than 50 μL for example. It would be useful to test small volumes or very small volumes of body fluids, especially if such testing could be performed contemporaneously with, or shortly after, obtaining the sample of body fluid.